Draw-press.



B. H. HAWKINS.

DRAW PRESS.

APPLICATION 111w JULY 6. 1914.

1,205,622. Paten ted Nov. 21, 1916.

w/rzvassaa 5 H/NVLZYTOR aw 1745 M By Ms ATTORNEY6 UNITED STATES PATENT OFFICE.

BERT H. HAWKINS, OF lOETRQI'l, MICHIGAN, ASSIGNOR TO McCORD MANUFACTURING COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MAINE.

DRAW-PRESS.

Specification of Letters Patent.

Application filed July 6, 1914. Serial No. 849,110,

To all whom it may concern:

Be it. known that I, BERT H. HAWKINS, a citizen of the United States, residing at Detroit,'in the county of WVayne and State of Michigan, have invented certain new and useful Improvementsin Draw-Presses; and I- do hereby declare the following to be a full, clear, and exact description of the in vention, such as will enable others skilled in the art towhich it appertains to make and use the same.

My invention relates to draw presses wherein cooperating dies are machine-operated to press metallic sheets into desired forms; and, generally stated, it consists of the novel devices and combinations of devices hereinafter described and defined in the claims. 1

In presses of the above-noted type, it has been customary to set the stripper plate on metallic or rubber springs, the resistance of which very rapidly increases under pressure, and the result of this is, that from the time the moving head of the press begins to depress the stripper plate, the pressure increases rapidly throughout the operative metal draw stroke. Otherwise stated, the force under which the stripper plate (sometimes designated as the presser plate) acts to press the metallic sheet against the mov-' ing head of the press, is materially variable in point of time, and uneven in its distribu' tion over the surfaces of the metallic sheet.

The present invention overcomes both of the above-noted defects, by providing means whereby yielding resistance in themovement of the stripper plate is made practically uniform, and'is efficiently distributed over the metallic sheet. These matters will be made clear from the following description of the operative press embodying my invention, and which is illustrated in the accompanying drawings;

In the said drawings, like characters indicate like parts throu hout the several views. Referring to the rawings: Figure 1 is a view in elevation with some parts broken away, showing the .improved press; and

. Fig. 2 is a fragmentary view partly in elevation and partly in vertical section on the line m 00 on Fig. 1.

The framework of the machine involves a heavy bed member 1 and a yoke-like pedestal 2 rigidly secured thereto. The movable head 3 of the press which carries the upper .one end of the crank shaft 6 is a large gear 7 that meshes with a pinion 8 on one end of e a counter shaft 9, journaled in suitable b'ear'- lngs on the pedestal 2, and provided at its op osite end with a' ulley 9, over which a be t, not shown, will e run to impart rotary motion to the crank shaft (3, and vertical movement to the head 3 and die 4. A lower and relatively fixed die 10.is supported on a bolster 11, which in turn is supported on the bed 1.

The numeral 12 indicates a short cylinder of relatively large diameter and which cylinder is fixed in respect to the bolster 11, being, as shown, suspended therefrom by hanger rods 13. \Vorking within the cylinder 12 is a piston 1a which supportsan expanded head 15, the upward movement of which is limited by the bolster l1.

The numeral 16 indicates a stripper'plate', which stripper plate is, as shown, made in a single piece, and is rectangular in form and of such size as to adapt it to be moved downward around the lower die 10. -This so-called stripper plate 16 is supported on the head 15 of the piston 14, as shown, by

means of vertical bolts 17, that pass through suitable openings in the bolster 11. When the piston is raised, as shown in the drawings, the upper surfaces of the stripper plate 16 will be slightly above the upper portion of the lower die 10. v v

The numeral 18 indicates an air equalizing tank which is connected by a pipe 19 to the lower portion of the cylinder 12.

The numeral 20 indicates an air pipe which leads from an air compressor, not shown, and taps the pipe 19, and hence, 18 connected to the equalizing tank 18.

The numeral 21 indicates a pressure gage shown as connected to the pipe 19.

The numeral 22 indicates a shut-off alve interposed in the pipe 19 between the said gage 2l and the cylinder 12.

' The numeral 23 indicates a relief 'valve which, as shown, is applied to one end of the pipe 19.

The numeral 24 indicates a shut-off vah'e in the pipe 20.

It.is, of course, understood that the sheet metal Work is given its form when the upper die 4 is pressed downward against the lower die 10. Normally, the work or n1c-- tallicsheet to be pressed, rests on the stripper plate 16, and it will be engaged by the upper die slightly before the said sheet or work is pressed into initial engagement with the lower die. The said stripper plate in is yieldingly supported by air introduced into the cylinder 12 under the piston 14. In practice, the valve 22 will-be opened to admit air into the said cylinder until the desired pressure is indicated" on the gage 21, and then the said valve 22 is closed, so as to confine the air under the desired pressure within the said cylinder. This yielding pressure permits the stripper plate to seat itself against the work with an even pressure at all points around the lower die, so that, as the .metal is displaced, it will be equally drawn in all directions. \Vhen the stripper plate is depressed in the drawing.

action as above indicated, the piston 14: will also be slightly depressed, and there will be a slight displacement of the air in the cylinder, but the resulting increased pressure will be so slight as to be negligible, for the reason, first, that the movement of the piston'is very slight, as compared with the diameter of the cylinder, and second, the air displaced from the cylinder equalizes with the air in the storage tank 18. The result of this is that the evenly distributed pressure on the stripper plate throughout the metal drawing action of the dies, is substantially constant, or in other words, for all practical purposes, is constant, -or not appreciably variable. This arrangement therefore, gives the ideal resisting pressure between the stripper plate and the work, or metal sheet being pressed, and very greatly improves the quality of work that may be done. In fact, with this improved arrangement, I have, in practice, found it possible to press a metal sheet to the desired form by one operation of the dies, whereas, the same kind of work performed on die presses, as hitherto arranged, would require-two successive die operations.

The so-called stripp r plate, which is also sometimes designated is a presser plate, will be made in a single'piece wherever such arrangement is practicable, but in otherinstances, it maybe made in sections. The cylinder and piston for supporting the stripper plate, constitute an expansible fluid-' pressure chamber, and this term is, therefore, used in a sense broad enough to include a device, such, for example, as a chamber equipped with a diaphragm instead of a piston.

What I claim is: I

1. In a draw press, the combination with cooperating dies and a stripper plate, of an air storage receptacle, and a movable element subject to air pressure delivered therefrom, supporting said stripper plate for limited movement, the capacity of said air storage receptacle being so great, in respect to the movement of said movable element and stripper plate, that variation in the fluid pressure in said storage receptacle and on said movable element, due to movements of the latter and said stripper plate, is ren-' dered negligible.

2; In a draw press, the combination with cooperating dies and a stripper plate, of an expansible fiuid pressure chamber yieldingly supporting said stripper plate, and an equalizing tank' connected to said expansible fluid pressure chamber.

3. In a draw press, the combination with cooperating dies and die operating mechanism, of a stripper plate cooperating with said dies, a fixed cylinder, a piston working in said cylinder and supporting said stripper plate, and an equalizing tank connected to said cylinder and having such capacity that the displacement caused by the movement of the piston raises the pressure only anegligible amount.

4. In a draw press, the combination :Witli cooperating dies and die operating mechanism, of a stripper plate cooperating with said dies, a fixed cylinder, a piston working in said cylinder and supporting said stripper plate, an air tank connected to said cylinder,- and a valved air supply pipe leading to said tank.

A 5. In a draw press, the combination with cooperating .dies and die operating mechanism, of a stripper plate cooperating with said dies, :1 fixed cylinder, a piston working in said cylinder and supporting said stripper plate, an equalizing. tank connected to said cylinder, a valved air supply'pipe-leading to said tank, and a pressure gage applied to indicate the equalized pressure in said cylinder and tank.

In testimony whereof Iaflix my signature in presence of two witnesses.

, BERT H. HAWKINS.

. Witnesses: w

' F. J. Kosra r, H. L. Hicks. 

